Biologists Study Impact of BP Oil Disaster On Loons

Just over a year ago, I held a “charismatic megavertebrate” on my lap. As a participant on a research project in the Gulf of Mexico just off the coast of Louisiana, I had tucked the common loon’s head under my left arm, secured its feet with my right hand, and held its body gently but firmly against mine as the boat we rode on raced back to shore. There, in an improvised lab under a bar on stilts, biologist Jim Paruk, who had just netted the bird, would quickly weigh, measure, band and assess the loon’s health before releasing it.

Like tigers, dolphins and bald eagles, common loons are considered charismatic megavertabrates because they are large, at least for birds, and tend to be well liked by the general public. On their breeding grounds in the far north—where the birds’ haunting calls have come to symbolize summertime in the wilderness—common loons also “may be the best-studied birds in North America,” says Paruk, senior scientist at the Maine-based Biodiversity Research Institute (BRI). He and his BRI colleagues alone have banded more than 4,800 loons in 22 states and seven Canadian provinces.

Winter Loon Mysteries

In winter, common loons molt to a dull plumage and vocalize very little. The bird on the left has been banded by researchers. Photo by Darwin Long.

Yet in the Gulf of Mexico and other places loons spend the nonbreeding season, very little is known about the birds’ behavior and ecology during winter. Not only do loons molt to a dull plumage in the colder months, they vocalize little, making it difficult for scientists to study them. Even local fishermen can be surprised to learn there are loons are in the Gulf. Point out one of the birds bobbing offshore and you’re likely to be told that it’s a cormorant.

Paruk and his colleagues are trying to uncover the secrets of winter loon biology—at least for birds that winter in and around Louisiana’s Barataria Bay. For the past four years, with funding from the Earthwatch Institute, Snow Family Foundation and BRI, the researchers have been making new discoveries about winter loons’ feeding, migration and other behaviors.

Sadly, their work also is beginning to suggest that loons may have been harmed more by the BP oil disaster than scientists previously realized. Because Barataria Bay was hit hard by the spill, Paruk’s teams have been taking blood samples from the birds they capture, looking specifically for polycyclic aromatic hydrocarbons, or PAHs. The class of hydrocarbons most toxic to wildlife, PAHs cause a range of health problems, including anemia, liver damage, cancer and immunosuppression.

Hydrocarbon Spike

During the first two years of the study, the number of loons with PAHs in their blood increased between 2011 and 2012, as did concentrations of the contaminants. Overall PAH levels remained low, however. But in 2013, reports Paruk in a recent article in National Wildlife,” we detected a large spike in PAHs and a completely different oil signature—heavy PAHs that are more toxic to wildlife.”

His findings are troubling. That loons had significantly more PAHs in their blood three years after the spill than immediately following it suggests that hydrocarbons may be making their way up the food chain, Paruk says. And unlike his first two years’ results, he adds, “the concentrations we found in 2013 may be high enough to cause physical harm.”

Last month, Paruk wrapped up his fourth field season in the Gulf. In addition to measuring PAH levels, the researchers this year are also analyzing blood for signs of Corexit, the chemical dispersant used to break up the spilled oil. (In Minnesota, scientists have found evidence of Corexit in white pelicans that were in the Gulf during the spill.) In addition, an immunologist will study the samples to see if the birds’ immune systems are damaged.

Where Are the Loons?

Riding in a small rubber raft, Gary Lackie captured this common loon off the coast of Alaska. Photo donated by National Wildlife Photo Contest entrant Gary Lackie.

While results of those analyses will not be available for several months, Paruk says he and his colleagues already have noticed something different—and potentially alarming—this year. “We encountered far fewer loons in the study area than in the previous three years,” he says. “There could be many reasons, some having nothing to do with the oil spill,” Paruk adds. Lacking long-term data on loon numbers in the Gulf, there may be natural population fluctuations that scientists are unaware of, for example.

Another possibility, however, is that loons affected by the oil spill may be producing fewer chicks on their northern breeding grounds, so fewer juveniles are showing up during winter. Next summer, Paruk will launch a new project in Canada to assess the status of breeding loons that winter off the Louisiana coast. If he finds signs of trouble, it will not be too surprising. “After all,” Paruk says, “we are still seeing impacts on Alaskan wildlife more than 20 years after the Exxon Valdez.”